Stud driving and testing mechanism



July 10, `1945. w. B. BRONANDER STUD DRIVING AND TESTING MECHANISM FiledNov. 5, 1942 7 Sheets-Sheet l ATTORNEY July 10, 1945- w. B. BRONANER2,379,878

STUD DRIVING AND TESTING VMECHANISM BY G OQ.

` ATTO NEY July 10, 1945. W. B. BRONANDER 2,379,878

STUD DRIVING AND TESTING MECHANISM Filed Nov; 5, 1942 7 Sheets-Sheet 5vlNvENToR Mlelwl?. Efawandaf R BY ;T ORNEY I July l0, 1945. w. B.BRONANDER 2,379,878

STUD DRIVING AND TESTING MECHANISM Filed No. 5, 1942 7 Sheets-Sheet 4 BYc L uATTO'NEY July 10, 1945 w. B. BRQNANDER 2,379,873

STUD DRIVING AND TESTING MECHANISM Filed Nov. 5, 1942 7 Sheets-Sheet 5 EBY ATT RNEY July 10, 1945. w. B. BRONANDER STUD DRIVING AND TESTINGMECHANISM Filed Nov. 5, 1942 7 Sheets-Sheet 6 7 R@L Y mM m ma m m W m wJuly 10, 1945. w. B. BRONANDER STUD DRIVING AND TESTING MECHANISM 7Sheets-Sheet 7 Filed Nov. 5, 1942 fav@ /Jy /55 /ff ATTORNEY PatentedJuly 10, 1945` UNITED STATES PATENT OFFICE i STUD DRIVING MECHANISMWilhelm B. Bronander, Montclair, N. J. 4Application November 5, 1942,Serial No. 464,626

(Cl. 8l57) 6 Claims.

This invention relates to stud driving and testing mechanism.

Studs are threaded at both ends and screwed and only studs having theproper size or flt can be utilized.

In the aircraft industry in particular, the proper mating of studs andstud holes is most important. It is essential that the studs be drivenin under not less than a certain, predetermineda torque, or the studsmay shake loose. Moreover, it is absolutely essential that the torquedrive does not exceed a predetermined limit as it has been found that ifthis torque is exceeded, after a certain number of hours of actualflight, the lugs or casing into which the studs have been screwed willcrack.

Government specifications, for this reason, set minimum and maximumtorque'limits. but all studs are tested by manually operated torquewrenches. Such operations give a chance for sabotage and itis verydlmcult to detect.

At the present time it isusual to screw the studs in by hand, usinglarge wrenches having sufficient leverage to furnish the necessarytorque required to screw the studs in tightly. If the stud is too largeit will not screw in to a suicient extent and must, therefore, beunscrewed and rcjected. n the other hand, if the stud is too small,relative to the size of the thread of the opening into which it isscrewed, it will not be tight enough and, therefore, must be unscrewedand rejected. oftentimes over size studs are broken off and must beremoved.

The procedure above outlined is laborious, time consuming and expensiveand, furthermore, is not productive of the required accuracy in sizingor grading the studs relative to the openings in which they are screwed.

This invention has for its salient object to provide a simple, practicaland eilicient method of selectively mating threaded studs to threadedopenings and to mechanism for canyingout this method.

Another object of the invention is to provide a method and mechanismwhereby oversize or undersize studs can be easily and quickly detectedand removed from the threaded openings in which they areY screwed andstuds of the required size can be quickly screwed into the openings withthe required torque.

Further objects of the invention will appear from the followingspecification taken in connection with the drawings which form a part ofthis application. and in which Fig. 1 is an elevational view ofthemachine constructed in accordance with the invention and adapted for usein carrying outthe method;

Fig. 2 is an elevational view, partly in longitudinal section, of thedriving end of the machine shown in Fig. 1;

Fig. 3 is a vertical sectional elevation taken substantially on line 3-3of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a sectional elevation through the control valve mechanismtaken substantially on line 4--4 of Fig. 2:

Fig. 5 is a vertical sectional elevation through the tool head, thisview being taken substantially 4 on line 5-5 of Fig. 9, looking in thedirection of the arrows, Fig. 5Nbeing on an enlarged scale;

Figs. 6, 7 and 8 are transverse sectional elevations through the toolhead taken substantially on lines 6-6, 1--1 and 8--8 respectively,,looking in the direction of the arrows;

Fig. 9 is an elevational view, partly in section,

taken at right angles to Fig. 5;

Figs. 10, il, 13, 14, 15, 17 and 18 are diagrammatic illustrationsshowing the various positions of adjustment ofthe driving connectionsand air control between the driving mechanism and the tool head Fig. 12is a vertical sectional elevation illustrating the inspectionsleevejbymeans of which the operator determines whether the stud hasbeen driven in too far with the minimum'torque drive; and if i ff Fig.16 is a view similar to Fig. 1,2 but showing the position of theinspection sleeve-after the stud has passed the minimum torque test andhas been driven in under maximumtorque, the posiltion of the sleeveindicating that the studfdiameter is too large.

The method, briefly described, consistsof driving the threaded stud intothe threaded opening with a torque drive up to a predetermined minimumtorque limit and to a predetermined depth, ejecting the stud if saiddepth is exceeded under minimum torque drive. If said depth is notexceeded the torquedrive is increased to a predetermined maximum and thestud is again driven into the hole to `a predetermined depth. .If said.depth is not reached the stud is ejected. If it ls thereby and if thestud satisfactorily withstands the minimum turque drive, maximum torquemay be applied thereto. Suitable testing means is provided whereby theoperator can easily and quickly determine whether the stud successivelywithstands the minimum and maximum torque drives.

Further details of the invention will appear from the followingdescription.

In the embodiment of the invention illustrated in the drawings, themachine for carrying out the method, as shown in Fig. 1, is mounted on asupport or base 25 which carries an upwardly extending casing 26 towhich are connected supporting brackets or casings 21 and 28.

The mechanism, as shown in Fig. 2, is driven by a motor M having a shaft29 on which is mounted a pair of gears 30 and 3|. The gear 30 mesheswith a gear 32 which is mounted on a ball bearing 33 carried by a sleeve34 which is mounted in the bracket 21. The gear 32 has a hub 35 on whichis formed or secured a driving disk 36 having a friction driving surface31. The disk 36 forms one half of a high speed clutch and is adapted todrive a disk 40 mounted on a bearing 4| and having formed thereon ahollow sleeve 42. 'I'he sleeve 42, as shown at 43, is pinned to a shaft44. 'I'he shaft 44 has formed integral therewith a hollow shaft 45 whichis mounted in suitable roller bearings 46 and 41.

The gear 3| meshes with a gear 48 -having a hub 49 mounted in a ballbearing 50. The gear 48 has a disk 5| formed integral therewith having afriction surface 52 adapted to coact with the other face of theintermediate clutch member or disk 40.

The intermediate clutch member or disk 40 is slidably or longitudinallymovable on its axis so that the member 40 may engage the high speedclutch disk 36 or the low speed clutch disk 5|.

Before describing the control mechanism by means of which the drive maybe shifted from high speed to low speed or vice versa, the drivingconnections between the hollow shaft 45 and the tool head will bedescribed.

The hollow shaft 45 has mounted thereon a worm gear 55 which meshes witha worm wheel 56 mounted on a shaft 51. The worm wheel 56 also mesheswith a gear 58 mounted on a stub shaft 59 in the casing 26. This casingis preferably provided with a suitable lubricant which is picked up bythe teeth of the gear 58 and is fed to the worm wheel 56 and worm gear55, thereby providing efcient lubrication for these parts.

The shaft 51, as shown particularly in Fig. 3, is mounted in suitablebearings 60 and 6|. Shaft 51 has secured to one end thereof a sprocketwheel 62 which, as shown in Fig. 1, is connected by a chain 63 to drivea sprocket wheel 64 mounted on a shaft 65 which is carried by the toolhead casing 66.

Tool head The tool head casing is swung on a parallel link connectionfrom the casing 26 in the following manner. A link is pivoted at 1| tolugs 12 carried by the casing 26 and is pivoted at its opposite end, asshown particularly in Fig. 9 at 13, to a pair of lugs 14 carried by thecover or casing of the tool head. The other links of the parallel linkconnection which supports the tool head casing are shown particularly inFigs. 1, 2, 3, 5 and 9. From these figures it will be seen that links 16are pivoted on the axis of the shaft 51 and at their other ends arepivoted at the axis of the shaft 65. By means of this parallel linkmotion the tool head can move downwardly to feed the screw into the workor upwardly away from the Work.

The shaft 65, as shown particularly in Figs.

5 and 9, has mounted thereon a worm gear 80 which meshes with a wormgear 8| mounted on a hollow shaft 82 supported in suitable bearings 83vand 84 in the tool head casing 66. The hollow shaft 82 has formedtherein longitudinal grooves 85 and 86, as shown particularly in Fig. 6.A cup shaped collar 81 surrounds a portion of the hollow shaft and isprovided with inwardly extending lugs 88 and 89 which seat in thegrooves 85 and 86. The cup shaped collar 81 is also provided withdiametrically opposite downwardly extending lugs 90 which engagecorrespondingly located and formed notches 9| formed in the uppersurface of a sleeve 92 which surrounds the lower portion of the hollowshaft 82 and extends below said shaft.

The cup shaped collar 81 is held downwardly so that the lugs 90 willengage the depressions 9| by springs 93 which seat at their lower endsin a cup shaped collar and at their upper ends against an abutment 94.

'I'he sleeve 92 has its lower end inwardly tapered, as shown at 95, toform a chuck or wedge which coacts under predetermined conditions toforce inwardly jaws 96 of a collet 91. The jaws 96 are provided withinternal threads 98 of a suitable pitch to receive one threaded end 99of a stud S. The other end of the stud is also threaded, as shown at|00.

'I'he collet 91 consists of a longitudinal sleeve which extends upwardlyin the sleeve 92 and is connected by a pin |0| to a plunger |02 slidablymounted in the hollow shaft 82. The pin |0| also secures within thecollet sleeve 91, a sleeve |03 which extends downwardly in the colletsleeve 91 and is internally threaded at |04. The threaded opening |04receives a threaded stud |05 which carries a stop pin |06 whichdetermines the extent to which the threaded end 99 of the stud S isscrewed into the collet or chuck. .The pin |06 is adjustable byvertically adjusting the threaded stud |05 in the threaded opening |04in the sleeve |03.

4The collet is driven from the sleeve 92 by means of the structureillustrated particularly in Figs. 5 and 8. As shown in Fig. 8, four lugs||0 are carried by the lower end of the sleeve 92. These lugs havereduced extensions which extend inwardly and form vertical ribs whichare received in vertical slots or grooves ||2 formed in the colletsleeve 91.

The lower end of the chuck or sleeve 92 has loosely mounted thereon acylindrical cup or sleeve ||3 having a retaining flange ||4 at its upperend and having an inwardly extendingflange ||5 at its lower end, theflange ||5 having a central opening I6 and extending beneath the lowerends of the collet jaws 96. These jaws are formed by upwardly extendingslots in the lower end of the collet sleeve 91. The manner of using thetesting sleeve or cup ||3 will be hereinafter described.

The plunger |02 is carried by a plunger head |20 mounted in a bearing|2I, the plunger being held in its upward position of movement by aspring |22. The head |20 and bearing |2| are mounted in an inverted cup|23 having a laterally extending flange |24. A piston |25 is mountedbetween a disk |26 and the flange |24 and is positioned in a cylinder|21 formed in the upper end of the tool casing. A suitable uid isadmitted to the cylinder chamberl |28, as hereinafter described, andwhen this iluid under pressure is admitted to the chamber |28, thepiston |25 is depressed in the cylinder |21 carrying with it the plunger|02. As the plunger is depressed, the collet and collet jaws are forceddownwardly in the sleeve 92, the chuck 95 causing the jaws to tightlygrip the threaded end -98 of the stud S which has been previouslyinserted in the collet jaws in a manner hereinafter described.

Since the drive between the shafts 85 and the hollow shaft 82 istransmitted through a worm gear drive mechanism, when the torque orresistance encountered as the stud S is screwed into the work exceeds apredetermined amount, the stud S can no longer rotate and the worm gear80 will tend to move longitudinally on a shaft 85.

.In order to prevent this movement, the mechanism shown in Fig. 9 isprovided. From this iigure it will be seen that the shaft 85, which ishollow, has threaded thereinto a stud or rod |30 on which is mounted aspring |3| which seats in a cup |32 at one end and at its opposite endagainst adjusting nuts |33 threaded on the stud |30. The spring tensionobtained by the use of the spring |3| will tend to prevent the relativemovement of the gear 80 to the left and axially of the shaft 85 asindicated by the arrow in Fig. 2.

Drive transmission and control mechanism This mechanism is lparticularlyshown in Figs. 2 and 4 and the settings for the operations performed areillustrated diagrammatically in Figs. to 18 inclusive. i

As shown in Fig. 2, the hollow shaft 45 has pinned thereto at |40, ashaft |4|. On the outer end of the shaft |4| is mounted on a ballbearing |42, a. cap |43 having an arcuate surface |44. A collar |45, cupshaped in cross section, is mounted on the shaft |4| and is held in thedesired position by adjustment by means of a nut |48 which is threadedonto the shaft |4|. Springs |41 `engage the cup shaped collar |45 andalso set in a flanged collar |48 which seats against the inner ball race|50 of the ball bearing 41 and rotates therewith. The springs |41 areadapted to provide a minlmum driving torque in the following manner.

Since the drive between the shaft 45 and the shaft 51 is transmittedthrough worm driving mechanism, when the stud :S'encounters apredetermined resistance, the worm gear 58 will be prevented fromrotating, thereby causing the worm gear 55, which is still being driven,to move lineally in the direction of the arrow in Fig. 2. Movement ofthe worm gear 55 in this direction will tend to cause the shaft 45 tomove toward the left, viewing Fig. 2, thus moving the intermediateclutch transmitting plate or disk y40 relative to the driving disk orclutch member 5|, to a suflicient extent to limit the torquetransmission to a predetermined setting. In order to permit the stud tobe screwed in to the desired extent or with a minimum torque drivingeifort, the springs |41 are provided. These springs, as clearly shown inFig. 2, tend to move the shaft 45 to the right viewing Fig. 2, thuspartially counteracting the tendency of the shaft to move toward theleft due to the slowing down or stopping of the worm wheel 58. Thesprings |41 are so chosen as to accomplish the foregoing result to thedesired extent.

This torque yielding or torque limiting action takes place on forwarddrive only. However, when the drive is in reverse the worm gear 55 willtend to move the shaft 45` to the right. viewing Fig. 2. Thus, thethrust reaction clamps the clutch disk 40 to the driving disk 5|, givingpractically a positive reverse drive. This is particularly importantunder a condition encountered when the stud has been driven in undermaximum torque but has not been driven, far enough into the work. It`has been found that after a stud has been driven in under predeterminedtorque a much greater torque is required to loosen and unscrew theVstud. By thus forcing the clutch disk 40 into tight engagement with thedriving disk 5| the necessary additional torque eifort required toloosen and remove the stud is provided.

The position of the shaft 45 and the intermediate clutch member 40carried thereby is determined by a cam |55 carried by a spindle or stubshaft |58 rotatably mounted in a bearing |51 formed in the bracket orcasing 28.

The cam |55 has formed thereon two concave cam surfaces |58 and 58 whichare separated by a ridge |80. Furthermore, the outer edges of theconcave surfaces |58` and |59 are bordered by ridges |8| and |82.

The cam |55 is manually controlled by a 'handle |83. When the cam ispositioned as shown in Fig. 2, the cap |43 is disposed opposite theconcave surface |59 which is so formed that the shaft 45 is positionedto permit theintermediate clutch member 40 to engage the clutch member5| and thereby transmit the drive from the shaft 28 to the shaft 45 atlow speed.

When the handle is moved to shift the cam |55 to the position shown inFig. 18 in which the ridge |80 engages the cap |43, the shaft 45 will beso positioned as to dispose the intermediate clutch member or drivenplate 40 between the clutch members 38 and 5| and thus no drive will betransmitted to the shaft 45.

When the handle and cam |55 have been shifted to the position shown inFig, 10 in which the cap |43 is disposed opposite the concave surface|58 and on ridge i6 i the shaft 45 will be shifted to the left, thusengaging the intermediate clutch member 48 with the clutch drivingmember 38, thus transmitting the drive at high speed to theshaft 45.High speed is also transmitted when the cam is shifted to the positionshown in Fig. 1l and the cap |43 is disposed in engagement with theridge |82.

In addition to controlling the position of the driven disk 40 withreference to the drivingdisks 38 and 5|, the cam and handle also controlthe passage of pressure uid to the tool head cylinder chamber |28. Thisis accomplished in the following manner.

As sho'wn particularly in Figs.'2 and 4, the cam |55 is rotatablymounted on a cylinder |85. A conduit |88 leads axially to the center ofthe cylinder and has connected theretoa supply pipe ||81 winch suppliesfluid under pressure thereto. From the central conduit |88 the fluidpasses radially through a conduit |58 to the periphery of the cylinder.The cylinder also is provided with a conduit |10 which communicates withthe periphery of the cylinder throughan opening |1| and alsocommunicates with a conduit |12 in the casing 28 in which the cam ismounted. A pipe |14` communicates with the conduit |12 and leads to thechamber |28, as shown in Fig. 5. A third conduit |15 is formed in thecylinder |85 and communicates through an opening |18 with the peripheryof the cylinder. Conduit |15 also communicates with a conduit |18 towhichl is connected anexhaust pipe |19.

In order to control communication between the various conduits withinthe cylinder |65, the cam |55 has formed therein a recess |80. Thisrecessl is arcuate in form, as shown in Fig. 2, and when the cam isadjusted, as shown in said flgure, the air or iiuid pressure from theconduit |68 passes through the recess |80 and through the opening |1|into the conduit |10 and thence through the conduit |12 and inlet pipe|14 to the chamber |28. As fluid under pressure is admitted to thischamber, the plunger |02 will be depressed, thus forcing the collet jaws96 into tight gripping engagement with the threaded end 99 of the studS.

When the cam is adjusted to the position shown in Fig. l0, the air inletor supply conduit |66 (Fig. 4) does not communicate with the conduit I10 or with the conduit |12 and inlet pipe |14. Thus no air reaches thechamber |28 and thejaws 96 will not be forced downwardly into the chuck.

After the minimum torque drive has been transmitted to the tool and thestud has not been driven in too far thereby, as will be hereinafterexplained, further torque or a maximum torque is applied in thefollowing manner. A bell crank lever comprising arms 85 and |86 ispivotally mounted, as shown at |81, on the bracket 21. 'I'his lever hasa downwardly extending lug |88 which is disposed opposite the outer endof a slidable stub shaft |89 positioned in axial alinement with theshaft 45. A spring |90 engages the outer end of the arm |86 and isadjustable by an eye bolt |9| which extends through the base member 25and is engaged by a wing nut |93.

The spring |90 tends to rotate the bell crank lever in an anti-clockwisedirection about the axis |81 and this rotation is normally prevented bymeans of a latch bar |94 which is pivoted at |95 to the outer end of thearm |85 and has at its opposite end a hook |96 which is adapted toengage a latch bar |91.

When the bar |94 is lifted, the spring |90 will rotate the bell cranklever in an anti-clockwise direction, causing the lug |88 to engage theouter end of the shaft |89 and to push this shaft inwardly against theouter end of the shaft 45, thus further resisting the tendency of thisshaft to shift to the left and discontinue the drive between theintermediate clutch member 40 and low speed clutch disk In this manner amaximum driving torque is permitted in driving the stud into the workbefore the drive is disconnected.

In order to unscrew the stud from the work in case the stud is not theproper size, a reversing switch R is provided for the motor M. Thisswitch operates in the usual well known manner to reverse the motor andthereby to reverse the drive.

Operation The cam |55 is moved by the handle |63 to the position shownin Fig. 10 in which the cap |43 on the right hand end of the shaft 45 isdisposed opposite the cam surface' |58 and on the ridge |6|. This causesthe shaft 45 to be shifted, engaging the intermediate clutch plate ordisk 40 with the high speed driving disk 36.

When the cam has been shifted to the position shown in Fig. 10, it willbe noted that the recess |88 in the cam establishes communicationbetween the conduits |16 and |10, thus opening the chamber |28 of thechuck cylinder |21 to the exhaust'. The fluid inlet conduit |68 thusdoes not communicate with the chuck cylinder and, therefore, the plunger|02 is not depressed and the collet is not forced down into the chuckinto driving engagement with the stud. The stud S is held by hand sothat the threads 99 on the upper end oi the stud will engage the threads98 on the collet jaws and the stud will be threaded inwardly at highspeed until the upper end thereof engages the pin |06 which forms astop.

After the stud has thus been inserted in the collet jaws, the cam |55 isshifted to the position shown in Fig. l1, in which the pressure conduit-|88 communicates with the conduit |10 through the recess and pressureiluid is thus fed to the chuck cylinder chamber |28, causing the piston|25 and the plunger |02 to be forced downwardly into the chuck, thusforcing the collet jaws vinwardly into driving engagement with the upperend of the chuck. It will be noted in Fig. l1 that the ridge |62 engagesthe cap |44, forcing the shaft 45 to the left, in which position theintermediate clutch member or driven plate 40 engages the high speeddriving clutch member 36. The stud will thus be driven into the workuntil it is slowed down and tends to resist turning.

The cam is then shifted to the position shown in Fig. 2. In thisposition pressure fluid is fed to the clutch cylinder and the colletjaws are clutched in the chuck. The stud will be driven at slow speedand the minimum torque drive effected by the action of the spring |41.The operator then tests the operation by the cap H3. If the cap isclamped tightly by the collet jaws against the work, Fig. 12, thisindicates that the stud has been driven in too far under the minimumtorque drive and thus does not properly fit the opening in which it isdriven. Under this condition the motor is reversed and the low speeddriving member 5| driven in reverse loosens the stud from the work. Ashereinbefore explained, the additional torque required for loosening thestud is available due to the fact that the worm gear tends to move theshaft 45 to the right, viewing Fig. 2, thus forcing the clutch disk 48into tight clamping relation relative to the driving disk 5|. Thepressure fluid holds the collet jaws to be clutched in the chuck. Afterthe stud is loosened, the cam is shifted to the position shown in Fig.14, in which fluid under pressure is supplied to the chuck cylinder andthe drive is transmitted at high speed, thus unscrewing the stud.

However, if after the stud has been driven in with the minimum torqueeffort the inspection cap ||3 is loose, as shown in Fig. 16, then themaximum torque is applied at low speed in the manner indicated in Fig.15. The maximum torque is applied by lifting the latch |94, thuspermitting the spring to shift the bell crank lever and through the lug|88 to apply force to the left hand end of the shaft 45. In Fig. 15fluid pressure is applied to the chuck cylinder and the drive istransmitted from the low speed clutch member 5|. y

If after the maximum torque is applied the cap ||3 is tightly clampedbetween the collet jaws and the work, this indicates that the stud doesnot exceed the maximum torque and the chuck is unscrewed from the studin the manner shown in Fig. 17. When the cam is adjusted, as shown inFig. 17, the cap |43 is engaged by the cam adjacent to the ridge |6I,forcing the driven or intermediate clutch plate 40 into engagement withthis high speed clutch driving member 36 and the uid pressure isdisconnected from the cylinder |21 in the manner above described inconnection with Fig. 10. During this last operation, as illustrated inFig. 17, the motor is reversed.

However, if the inspection cap is loose, as after maximum torque hasbeen applied to drive the stud inwardly, this indicates too large andthe motor is reversed and the stud is unscrewed from the work in themanner indicated in Figs. 13 and 14.

Fig. 18 illustrates a condition where the drive is in neutral position,the cap |43 being disposed in engagement with the ridge |60. Theintermediate clutch member or driven plate 40, as shown, is disposedbetween the high speed driving member 36 and the ber no drive beingtransmitted to the driven shaft 45. In this ilgure no pressure iiuid istransmitted to the clutch cylinder |21.

In the manner hereinbefore described, it will be seen that the stud isrst driven in with a minimum driving effort and if the inspection cap isnot clamped tightly, the latch |94 is lifted to apply the maximumdriving eii'ort at slow speed. If after this operation the inspectioncap, is loose, it indicates that the stud is too large and must beremoved in the manner described. However, if the inspection cap isclamped tightly between the collet jaws and the Work, this indicatesthat the stud has the proper fit and the unscrewed, leaving the stud inposition.

It will be evident that the operations above outlined can be carried outeasily and quickly and that a deiinite and positive check is availableto the operator to indicate whether the stud is the proper size to iitin the opening in which it is screwed with a maximum driving torque.

low speed driving meml Although one speciiic embodiment of the inventionhas been particularly shown and described, it will be understood thatthe invention is capable of modiiication and that changes in thearrangement and in the construction ci the various cooperating parts maybe made without departing from the spirit or scope oi the invention, asexpressed in the following claims.

What I claim is:

1. A stud screwing and testing machine comT prising a chuck, chuckdriving means for driving the chuck and stud carried thereby, saiddriving driven too far into the studreceiving opening, and testing meansengageable by the operator and comprising a sleeve rotatably mounted onthe chuck'and having the chuck and erator the fit of the stud in thehole and the extent to which the stud has um torque drive.

2. A stud screwing and testing machine com- Drising a chuck, chuckdriving means for driving the chuck and stud carried thereby, saiddriving means including a releasable driving connection and means forholding said connection in operative position to transmit a minimumtorque eiIort, laid driving connection being inoperative beyond saidminimum torque, manually controlled means associated with said drivingconnection for increasing the torque driving effort it the stud has beendriven under withstood the minimum torque drive without being driven toofar into the stud receiving openings, and testing means engageable bythe operator and comprising a sleeve rotatably mounted on the chuck andhaving a. portion extending between the chuck and the work forindicating to the operator the extent to which the stud has been drivenunder minimum torquedrive and under maximum torque drive.

3. A stud screwing and testing machine comprising a chuck, chuck drivingmeans for driving the chuck and stud carried thereby with apredetermined minimum torque effort, said driving means beinginoperative beyond said minimum torque, manually controlled means forincreasing the torque driving eii'ort if the stud has withstood theminimum torque drive without being driven too far into the studreceiving opening, and testing means comprising a, cap loosely carried.by and rotatable relative to the chuck and extending beneath the chuckand engageablewith the work a predetermined extent for indicating to theoperator the fit of the stud in the hole and the ex;- tent to which thestud has been driven under minimum torque drive'.

4. A stud screwing and testing machine com'- prising a chuck, chuckdriving means for driving the chuck and stud carried thereby with apredetermined minimum torque efiort, said driving means beinginoperative beyond said minimum torque, means for increasing the torquedriving effort if the stud has withstood the minimum torque drivewithout being driven too far into the stud receiving opening. andtesting means comprising a cap loosely carried by and rotatable on thechuck and having a portion extending under the bottom of the chuck andengageable with the work when the stud has been screwed in to apredetermined extent for indicating to the operator the extent to whichthe stud has been driven under minimum torque drive and under maximumtorque drive.

control mechanism for controlling said clutch and for controlling thecarried by the chuck thereon and having a portion extending below thechuck and between the chuck and the work and adapted to be clampedbetween the chuck and tent to which the stud has been driven and the fitoi the stud in the work.

WIT-:HELM: B. BRONANDER.

when the stud has been screwed in to

